Durable, flexible materials are often used as skins or coverings that are applied to an internal physical structure. For example, silicone rubber is often used to create realistic models of humans, animals, and fantasy characters, and when combined with robotics, such models can accurately simulate live animals, persons, or characters.
The design of such skins presents a particular unique challenge. Specifically, the skin must be robust enough to withstand prolonged used and exposure to environmental conditions. The skin must also be realistic in appearance, movement, and texture to accurately imitate the person or animal it resembles. The skin must also be easily formed and easy to handle and attach to a physical support structure or skeleton. To create a realistic appearance and deformation, soft elastomers are typically used to create skin. Some elastomers, such as silicone rubber, can be painted by applying pigment to an outer surface. However, painting can hide or modify the outer texture of the skin, which may affect the desired appearance. Additionally, silicone rubber is often quite heavy, which requires powerful robotics to move the internal structure to which the skin is attached.
Many thermoplastic elastomers, such as styrene-butadiene rubber, are lighter weight than silicone rubber and have mechanical properties that are often preferred for animatronic structures. For example, styrene-butadiene rubber is more flexible and can stretch easier than silicone rubber. However, the increased elongation that allows for the increased flexibility also causes paint to peel off or otherwise not adhere to styrene-butadiene rubber for long periods of time, eliminating painting as a viable option for coloring the material. Some thermoplastic elastomers can be colored using “negative painting” techniques where the material is molded with another colored material to create a colored structure. Negative painting techniques are time consuming, difficult to use to create multi-colored materials, and very difficult to use to create highly detailed colored designs. As such, although thermoplastic elastomers such as styrene-butadiene rubber, have preferred mechanical properties as compared to conventional skin materials, they have not been used due to inability to efficiently and permanently color the materials.